The objective of the Energy Balance Core Laboratory (hereafter referred to as the Core) is to provide expertise and state-of-the-science instrumentation and techniques for measuring aspects of energy balance for obesity- and nutrition-related basic, clinical, translational, and multi-disciplinary research at the UCD and its affiliates. The services of the Core have been essential for a large number of investigators in the CNRU research base. Because many of the studies supported in the past 5 years involved obesity research, the transition from CNRU to NORC will occur seamlessly and the new title of the Center will more accurately describe the research base that has been supported. The consolidation of the instruments and techniques used by multiple investigators in the Core laboratories is desirable because of the high cost of some of the equipment and the extensive training and expertise of personnel required to appropriately operate and maintain the equipment. There are many sophisticated tools available for measuring components of energy balance. The Core Laboratory was established to ensure that CNRU investigators have access to the best possible tools and techniques for studying energy balance. The Core provides help to investigators in choosing the method that is most appropriate for the intent and scope of their research. For example, the wholeroom calorimeter is a highly accurate tool for measuring energy expenditure. However, its use requires careful measurement of nutrient intake and control and measurement of energy expenditure and physical activity before subjects enter the calorimeter. Because this is not feasible or necessary for many studies, a metabolic cart can often provide the needed information with less commitment of time and resources. Several investigators who requested use of the whole-room calorimeter ended up using a metabolic cart at much lower cost to obtain the information they required.